Turning first to gas systems for firearms, gas-operation is a system used to provide energy to operate auto-loading firearms. In gas-operation, a portion of high pressure gas from the cartridge being fired is used to power a mechanism to extract the spent case and chamber a new cartridge. Energy from the gas is harnessed through either a port in the barrel or trap at the muzzle. This high-pressure gas impinges on a movable surface such as a piston head to provide motion for unlocking the action, extracting and ejecting the spent case, cocking the hammer or striker, chambering a fresh cartridge, and locking the action.
Most current gas systems employ some type of piston. The face of the piston is acted upon by gas from the combustion of the propellant from the barrel of the firearm. Early methods such as Browning's ‘flapper’ prototype, the Bang rifle, and Garand rifle used relatively low-pressure gas from at or near the muzzle, where the bullet exits the barrel. This, combined with more massive operating parts, reduced the strain on the mechanism. To simplify and lighten the firearm, gas from nearer the chamber needed to be used. This gas is of extremely high pressure and has sufficient force to destroy a firearm unless it is regulated somehow. Several methods are employed to regulate the energy. The M1 carbine incorporates a very short piston, or “tappet”. This movement is closely restricted by a shoulder recess. Excess gas is then vented back into the bore. The M14 rifle and 60 GPMG use the White expansion and cutoff system to stop (cut off) gas from entering the cylinder once the piston has traveled a short distance. Most systems, however, vent excess gas into the atmosphere through slots, holes, or ports.
With a long-stroke system, the piston is mechanically fixed to the bolt group and moves through the entire operating cycle. This system is used in weapons such as the Bren light machine gun, AK-47, Tavor, M249 Squad Automatic Weapon, FN MAG, M1 Garand, and various semi-automatic shotguns, for example. The primary advantage of the long-stroke system, beyond design simplicity and robustness, is that the mass of the piston rod adds to the momentum of the bolt carrier enabling more positive extraction, ejection, chambering, and locking. Also, as the gas is not directed back into the chamber, the weapon stays cleaner longer thus reducing the likelihood of a malfunction.
By way of example, the functioning of a standard long-stroke gas-operated firearm such as the AK-47 will be described in detail. AK-47 rifles are so-called gas powered firearms, in which the discharge gases from a fired round of ammunition serve to automatically eject the spent cartridge casing from the just-fired round and to chamber a new round for firing. The standard charging mechanism of an AK-47 comprises a barrel in communication with a firing chamber, or breach, and a bolt used to provide access to the breach. The barrel comprises a port or similar aperture which permits some of the discharge gases created from the firing of a round of ammunition to escape the barrel through the port. The port is in communication with an adjacent chamber known as a gas block, which in turn is in communication with an adjacent, substantially cylindrical structure known as a gas tube. Contained within the gas tube is a gas piston assembly known as an operating rod. The operating rod has a forward portion comprising a piston with an outside diameter substantially the same as the inside diameter of the gas tube. The rearward end of the operating rod is in connection with the bolt carrier assembly. The operating rod and carrier assembly is designed to move forward and rearward within the gas tube, with its rearward movement designed to simultaneously force the bolt assembly rearward, which in turn compresses a recoil spring mechanism. The recoil spring mechanism in turn forces the bolt assembly forward, returning it to its firing position, which in turn moves the operating rod forward within the gas tube.
A standard AK-47 must be charged in order to operate. Charging of the firearm comprises the loading and reloading of ammunition into the firing chamber and occurs during the rearward and forward movement of the bolt assembly described above. During operation, charging is done automatically by utilizing the discharge gases of a fired round of ammunition. When a round is fired, the cartridge casing remains at one end of the barrel and the gases formed by the explosion force the bullet to travel down the length of the barrel. As the bullet passes the barrel port, some of the discharge gases escape through the barrel port and pass through the gas block into the gas tube, where the gases impinge upon the forward portion of the operating rod, driving it rearward. This rearward travel of the operating rod moves the bolt rearward, opening the breach, ejecting the spent cartridge casing from the breach, and compressing the recoil spring mechanism in connection with the rear portion of the bolt. While the bolt is thus in its rearward position and the breach is opened, a new round may be loaded into the breach by action of a spring mechanism in an ammunition magazine. The bolt is returned to its forward position by the recoil spring mechanism, closing the breach and returning the operating rod to its forward position. This process may continue by continuing to pull the trigger until all of the ammunition is used and the ammunition magazine and the firing chamber are both emptied.
Simplified section views of a typical long-stroke gas-operation system in use are depicted in FIGS. 1A-1E. A typical long-stroke gas-operation system 100 of a firearm may comprise a barrel 105 having a gas port 110 located distally down the barrel 105, well away from the chamber 170. The gas port 110 vents part of the pressurized gas 165 resulting from the firing of gunpowder 155 causing a bullet or other projectile(s) 150 (herein collectively, “bullet 150”) to travel down the barrel 105 from a proximal end near the chamber 170 to a distal end where the bullet exits the barrel 105 through a muzzle (not shown). The gas port 110 typically vents a small portion of the pressurized gas 165 into an adjacent cylinder 115 just beyond a piston 120 located in the cylinder 115, as depicted in FIGS. 1B-1D. The piston 120 is typically connected by a piston rod or operation rod 125 to a bolt carrier 130, those parts together comprising a carrier assembly that typically slides in the opposite direction of the bullet 150 (i.e., rearward, or to the right in FIGS. 1-4 and 7-8B) when the pressurized gas 165 travels down the barrel 105 behind the bullet 150, through the gas port 110, into the cylinder 115, and impinges on the face of the piston 120, as depicted in FIGS. 1B-1D. The momentum of the rearward travel of the bolt carrier assembly typically causes the bolt carrier 130 to unlock a locking block 145 that locks the bolt 140 to the chamber 170 (i.e., unlocks the “action”), and then the bolt carrier 130 pushes the bolt 140 backwards (to the right in FIGS. 1-4 and 7-8B) away from the chamber 170, while expelling the spent casing 160 and introducing a new cartridge with bullet 150 into the chamber 170, as depicted in FIG. 1E. The rearward travel of the carrier assembly is typically increasingly resisted by a spring 135, which then urges the carrier assembly to travel back in the forward direction (to the left in the Figures, FIG. 1F), re-locking the bolt 140 to the chamber 170, whereupon the firearm returns to the position shown in FIG. 1A, ready to fire again.
One disadvantage of this type of system 100 is that, due to the significant mass of moving parts, a significant amount of high-pressure gas 165 is required to operate the system 100. In order to transmit the required volume of high-pressure gas 165 to the piston 120, manufacturers utilize various numbers of gas ports 110 of different sizes, typically located near or distally (to the left in the Figures) of the resting position of the piston 120 to allow the high-pressure gas 165 to flow backward (to the right in FIGS. 1-4 and 7-8B) against the face of the piston 120. There are some key limitations to this type of system 100. First, these small ports 110 are prone to clogging due to debris created when a round or bullet 150 is fired. Clogged ports 110 can cause the firearm to cease functioning as intended.
Second, the size and/or number of ports 110 can directly affect the types of loads that can be used. If the ports 110 are small or there are few of them it is more difficult for high-pressure gas 165 to be redirected to the piston 120. This results in the firearm requiring heavy loads (high-powered cartridges) in order for the gas-operation system 100 of the firearm to cycle. Alternatively, if ports 110 are larger or more numerous then gas 165 is more easily redirected, which can allow the firearm to cycle lighter loads (lower-powered cartridges). However, where large ports 110 are used, heavy loads may cause excessive wear on the firearm due to exposing the face of the piston 120 to an excessive volume of high-pressure gas 165 directly from the interior of the barrel 105.
A third limitation of typical systems 100 is the distal location of the ports 110. By placing the ports 110 in a distal portion of the barrel 150 (distally from the firing chamber 170) adjacent or beyond the resting position of the piston 120, the pressure of the high pressure gas 165 available at the ports 110 is greatly reduced and is widely variable depending on the power of the cartridge 150. Thus, present systems 100 provide inefficient and inconsistent capturing and transmission of high-pressure gas 165.
Turning next to quick-release-barrel modular systems for long-stroke gas-operated firearms, such systems are known with respect to manual-feed firearms that do not use a gas system, such as bolt-action rifles, double-barreled shotguns, pump shotguns, and lever-action rifles. Providing a quick-release-barrel modular systems for gas-operated firearms is more complex, however, since the barrel is typically integrated with part of the gas system. The M-16/AR-15 rifle is a common example of a gas-operated firearm with a removable barrel assembly. The M-16/AR-15 rifle achieves its modularity by splitting the upper and lower receivers; i.e., when removed, the barrel remains attached to the upper part of the receiver. Moreover, the M-16/AR-15 rifle is not a long-stroke system like the AK-47, so there is no carrier rod/assembly in a gas cylinder that is integrated with and adjacent to the barrel. When there is no carrier rod/assembly adjacent the barrel, quick-disconnect systems are easily employed using threaded barrels or any variety of mechanisms, usually involving rotating the barrel assembly with respect to the receiver. But when there is a carrier rod/assembly in a gas cylinder that is integrated with and adjacent to the barrel as in long-stroke gas-operated firearms such as the AK-47, M60, or M249, the barrel assembly cannot be rotated relative to the receiver. Further, removal of the barrel from such long-stroke gas-operated firearms requires that the user first remove the bolt carrier and operation rod from the receiver. Accordingly, no truly quick-disconnect system exists for removing the barrel assembly from the receiver assembly of long-stroke gas-operated firearms.
Turning now to improved forward-charging handle systems, the automatic loading cycle of each round of ammunition described above with respect to FIGS. 1A-1F takes place upon the firing of the previous round. However, the initial charging of the firearm in which the first round is loaded into the firing chamber must be accomplished manually, as no discharge gases have yet been created to accomplish this task. Initial charging of a standard AK-47 is accomplished by manually drawing the bolt assembly rearward or in the proximal direction (toward the user). This is done by manually grasping and drawing back a charging handle which is in connection with the bolt assembly and located on the right side of the firearm. Drawing the charging handle rearward results in the same loading of the round into the breach by the spring mechanism in the ammunition magazine as described above. Releasing the charging handle allows the recoil spring mechanism to return the bolt to its forward position, closing the breach, resulting in the firearm being loaded and ready for firing.
Among other things, conventional charging handles for AK-47s are located inconveniently and move back-and-forth forcefully and rapidly as the weapon is fired, posing a risk of injury to the user. Charging handles for AK-47 and other popular gas powered firearms, such as the various Kalashnikov variants (AK-74, AK-101, AK-103, and others), the Samozaryadniy Karabin sistemi Simonova (SKS) rifle and its variants, and the Fusil Automatique Leger-Light Automatic Rifle (FN-FAL) and its variants, as well as other designs, have various other drawbacks as described in U.S. Pat. No. 8,141,474 B2 to Dublin, filed Aug. 13, 2009 and issued Mar. 27, 2012 (herein “Dublin”), the entirety of which is incorporated herein by reference. While Dublin proposes a solution to address some of these issues, the charging handle system described in Dublin would have to be disassembled before removing the barrel, thus rendering it unusable with quick-release-barrel modular systems. What is needed is a charging handle system that provides the benefits of the Dublin system, but that can also be used with quick-release-barrel modular systems.